The present invention relates to a heating device for a vehicle lamp and, more particularly, to a heating device for heating a vehicle lamp without blocking the main light output of the vehicle lamp while providing an excellent heating effect.
A vehicle generally includes vehicle lamps, such as headlamps, tail lamps, turn signals, and fog lamps, for illumination and warning purposes. However, snow could accumulate in the vehicle lamps in a snow condition and could block the light output. In an approach to solve this problem, a heating device is mounted in currently available vehicle lamps.
U.S. Pat. No. 8,899,803 discloses a headlamp including a housing, a heat dissipating mechanism, a main circuit board, two light emitting diodes, a lens, a wire heating element, a circuit board for the wire heating element, and an encapsulating layer. Two reflectors are mounted in the housing for producing high-beam and low-beam outputs. The two light emitting didoes are mounted in locations associated with the two reflectors. The heat dissipation mechanism is coupled to the two light emitting diodes and is electrically connected to the main circuit board. The lens is mounted in front of the housing. The circuit board for the wire heating element is mounted on the lens. The encapsulating layer is disposed over the wire heating element. The wire heating element is disposed on a central portion of the inner surface of the lens and is electrically coupled to the circuit board for the wire heating element.
In a snow condition, the circuit board for the wire heating element makes the wire heating element generate heat, generating heat energy for directly heating the central portion of the lens, such that the snow on the central portion on the outer surface of the lens can melt and fall, thereby avoiding hindrance to the light output.
However, the wire heating element is mounted on the central portion of the inner surface of the lens which is in the output path of the light rays of the two light emitting diodes after reflection by the two reflectors, such that the output luminance is reduced. The heating effect is reduced if a thinner wire heating element is used for reducing the hindrance to the output luminance. Furthermore, the structure including the main circuit board and the circuit board for the wire heating element has complicated components. Furthermore, the circuit board for the wire heating element mounted on the lens occupies the light-transmittable area.
U.S. Patent Nos. 6,563,286; 7,410,257; 7,553,053; and 8,459,848 and U.S. Patent Publication Nos. US20060011598 and US20010181565 also disclose a heating wire directly mounted to a central surface of a lens and include the same disadvantage of hindrance to the light output.